Flame of Recca is actually done by the producer of Yu Yu Hakusho I believe. Flame of Recca takes around one volume to really get interesting but once the "true" storyline begans after the character introduces, you'll love the series. I still like to point out that Recca is more ninja then Naruto, read the series and see what I mean.
Black Cat has its up and down moments, the first volume is excellent on setting up the storyline but halfway through the middle of the series. You get a feeling of wishing that the main storyline will continue, although that little dought only last around three to four chapters tops.
Mainly download the first two volumes of both series's to see if you like them.